Despite success of anti-retroviral therapy (ART) against HIV infection, viral mutations continue to diminish its therapeutic efficacy necessitating new approaches. One such approach is to harness virus/host interactions to potently repress HIV replication. Using this approach, we recently reported that active Wnt/???-catenin signaling in infected cells represses HIV replication. The Wnt pathway regulates ~500 genes involved in cell differentiation, proliferation, migration, communication and apoptosis. This pathway can be activated by lithium, which represses glycogen synthase kinase 3 (GSK-3), a negative regulator (inhibitor) of Wnt signaling. The ability of lithium to activate Wnt/? -catenin signaling makes it a convenient tool with which to investigate interactions between the Wnt/??-catenin pathway and HIV replication. Using this tool, we found that incubation of HIV-infected peripheral blood mononuclear cells (PBMCs) with noncytotoxic, noncytostatic concentrations of lithium reduced replication of HIV T-tropic and primary isolates by >90%. Inhibition of Wnt/2-catenin signaling by transfection of dominant negative mutant constructs to either T cell factor-4 (TCF-4), the down-stream effector of Wnt signaling, or ?-catenin, the central mediator of this pathway, (i) abrogated the ability of lithium to inhibit HIV replication and (ii) increased HIV replication. These data suggest that the Wnt/?-catenin is an intrinsic signaling pathway that represses HIV replication and is a mechanism by which lithium exerts its anti- HIV effect. We now propose further investigation of this potential new ART approach. In Aim 1 we will determine the mechanisms underlying ?-catenin-mediated inhibition of HIV replication in PBMCs. Our hypothesis is: Induction of Wnt/?-catenin inhibits HIV replication in PBMCs by inducing TCF-4 binding to an HIV TAR spanning region that will interfere with Tat-mediated LTR transactivation. In Aim 2 we will determine the external validity of the mechanism investigated in Aim 1 by determining the extent of Wnt/?-catenin- mediated suppression of HIV replication in other permissive targets -primary CD4+ T cells, monocyte-derived macrophages and microglia. Validation of our hypothesis would (1) provide proof of concept that stimulation of ?-catenin/TCF-4 (Wnt) signaling inhibits HIV replication;(2) reveal mechanisms by which it does so. This would lead to (3) a better understanding of Wnt/?-catenin interactions in HIV infection, and to (4) new approaches to ART in HIV-infected individuals. In particular, it would expedite development of (a) agents that activate ?-catenin/TCF-4 signaling as potential inhibitors of HIV replication and (b) basic and clinical models for testing such agents. All this could lead to novel anti-retroviral interventions. PUBLIC HEALTH RELEVANCE: Exploring the interaction between HIV and host proteins can lead to the development of new generation of HIV drugs. We identified a host signaling pathway, known as the Wnt/beta catenin pathway, which leads to potent suppression of HIV replication. This pathway can be turned on by the generic drug lithium. We found that when the pathway is turned on, HIV replication is inhibited by >90%. When the pathway is turned off, HIV replication is induced by 4-fold. Taken together, these data indicate that this pathway is a regulator of HIV replication. The purpose of this exploratory grant is to identify how this pathway represses HIV replication (Aim1) and if this pathway can also lead to HIV suppression in various cell types, including those in blood and brain (Aim 2). These studies are important because they will identify host/virus interaction that can lead to the development of novel HIV therapeutics to be used alone or in combination with current anti-HIV therapy.